Process for preparing organotin halides



United States Patent 3,404,167 rnocnss FOR PREPARING ORGANOTKN HALIDESRobert D. Gray, Gloucester, and Simon E. Mayer, Lexington, Mass,assignors to Argus Chemical Corporation, Brooklyn, N.Y., a corporationof New York No Drawing. Filed Nov. 30, 1964, Ser. No. 414,841 12 Claims.(Cl. 260-4293) ABSTRACT OF Til-IE DISCLOSURE This invention relates toan improved process for the preparation of organotin compounds, andespecially organotin halides. More particularly, the invention pertainsto an improved process for the preparation of alkyl or aryl tin halidesas well as novel reactants therefor.

One of the methods employed for many years in the preparation oforganotin compounds was the direct reaction of metallic tin with alkylhalides. This reaction had certain commercial limitations insofar as itwas possible only by utilizing the lower alkyls. Moreover, high yieldswere only achieved by the use of alkyl iodides, with lower yieldsresulting even from the use of alkyl bromides. The use of tin alloys inplace of the tin is a variation of this basic reaction. The preferredalloy for this purpose was sodium-tin alloys, although more recentlymagnesium-tin alloys have also been proposed. Prior art teachingsindicated that the use of such alloys is limited to those alloys whichare sufiiciently brittle to be reduced by grinding operations to asuitable form prior to employment in the process. It has been furtherfound that the use of such alloys or metallic tin, even in the presenceof catalysts, leads to progressively lower yields as longer chain lengthalkyls are employed and as the halides are changed from the iodides tothe bromides and then to the chlorides. In fact, for the commercialmanufacture of butyl tin halide compounds, which have assumedconsiderable commercial importance, it has not been economicallyfeasible to use as feed material butyl chloride but only the bromide.Even then the reaction was slow, and the process was severely limitedbecause tin foil had to be used as a source of the tin.

U.S. Patent No. 2,852,543, issued to Blitzer et al. on Sept. 16, 1958,relates to a process for the preparation of alkyl tin chloridesutilizing sodium-tin alloys, and preferably the monosodium tin alloy,NaSn. The Blitzer et al. process requires a reaction temperature of atleast 140 C. and pressure conditions to ensure that the alkyl chlorideis maintained in a liquid state. The patentees state that the use of acatalyst such as zinc in their process is permissible and frequentlydesirable. The advantages of the Blitzer et a1. process over the priorart Grignard process and the prior art proposals resulting from the useof sodiun1-tin alloys is discussed in column 1 of US. Patent No.2,852,543.

One object of the present invention is to provide an improved processfor the preparation of alkyl or aryl tin halides which avoids thedifiiculties encountered in the prior art processes.

3,404,167 Patented Oct. 1, 1968 Another object of the present inventionis to provide an improved process for the preparation of alkyl or aryltin halides which utilizes a special form metallic tin as one of thereactants.

A further object of the present invention is to provide a process forthe preparation of alkyl or aryl tin halides which does not require thespecific operating conditions prescribed in certain of the prior artprocesses.

A still further object of the present invention is to provide novel tinreactants which can be effectively utilized in various reactions such asthe preparation of alkyl or aryl tin halides from alkyl or aryl halidefeed materials, respectively.

An additional object of the present invention is to provide novel tinreactants which can be reacted with alkyl halides in an improved processto outstanding yields of the desired dialkyl compounds as compared tothe trialkyl and tetraalkyl compounds.

These and other objects of the present invention will become readilyapparent from the ensuingdescription and the illustrative embodiments.

In accordance with the present invention it has now been found thatvarious alkyl or aryl halides, including alkyl chlorides havingrelatively long chain lengths, can readily be reacted with tin toproduce the desired alkyl or aryl tin halides, provided that the tin isemployed in extremely finely divided and oxide-free form. The finelydivided tin has to have a particle size ranging from about 1 to 300microns, and preferably from about 5 to 40 microns. It will beunderstood that the exact method utilized in preparing the finelydivided tin is not a basic feature of this invention. Nevertheless, ithas been found that metal spraying methods wherein the tin is atomizedare particularly eifective for producing the finely divided tin requiredin the instant process. It is also preferred to atomize the tin in aninert atmosphere such as helium, argon, or less desirably nitrogen, andthe like to avoid surface and internal oxide or other contamination. Itis also preferred to maintain the finely divided tin under the inertatmosphere prior to use such as during storage, transfer, etc.

In one aspect of the present invention it has been found advantageous toactivate further the reactive finely divided tin particles describedabove by the use of alkali metals such as sodium, potassium, lithium ormixtures thereof. The preferred alkali metal for this embodiment issodium. In general, the finely divided tin can be activated by treatingthe atomized or finely divided tin with an alkali metal under suchconditions that the surface of the tin particles is activated and anyexcess sodium is converted to the sodium-tin alloy. One possible methodfor accomplishing this surface activation by use of alkali metalsinvolves the use of the fluidized bed technique. Broadly, this techniquecomprises the agitation of the metal powder in a vertical column bymeans of an inert gas such as helium or argon. The gas is introducedinto the bottom of the column through a porous plate. Both the gas andthe walls of the column are heated to a suitable temperature above themelting point of sodium and below the melting point of tin, e.g. C. Therequired amount of sodium is then introduced slowly, generally in liquidform, preferably into the center of the column so that it is evenlydivided over the surface of the metal powder in the column. The sodiumcleans and activates the surface of the-tin and any excess sodiumpresent reacts with the latter to form sodium tin alloys. The presenceof excess sodium which is not combined as the tin sodium alloy is highlyundesirable. It should be understood that such columns can be operatedeither on a batch or on a continuous basis.

In the activation of the tin particles with alkali metals it isemphasized that only the surface of the tin particles is converted tothe sodium-tin alloy; the bulk of the tin remains in the metal form. Insome instances it is desirable to obtain further improvements by heatingthe thus treated finely divided tin particles at temperatures above 100C., and preferably within the range of about 150 C. to 200 C., for atime period, e.g. at least 2 hours at the lower temperatures and atleast minutes at the higher temperatures, to obtain some superficialdiffusion of the alkali metal into the bulk of the tin particles inorder to eliminate any traces of tin oxide that may be present, and toeliminate alloys of high sodium content from the surface which onreaction with the alkyl halides yield the less desirable trialkyl andtetraalkyl compounds.

The total amount of alkali metal employed in activating the tinparticles may range from about 1 to 35% by weight, based on the totalweight of the tin particles. For most purposes, however, it is preferredto utilize from about 1 to 5% by weight of the alkali metal; andexcellent results have also been achieved when the total amount ofalkali metal in the activated tin particles ranges from about 1 to 3%.In accordance with another aspect of the present invention, variousmethods can be employed to activate the surfaces of the tin particles.For example, the tin may be dispersed as fine particles, in the range ofabout to 40 microns, into an inert liquid. Other possible techniqueswhich may be used, either alone or in conjunction with differentmethods, include mechanical abrading, etching, drastic alternate heatingand cooling techniques, and similar chemical or physical processes whichtend to release the surface strain on the active tin surface. It hasbeen found desirable in some cases to employ an iodine-containingcatalyst to initiate the alkylation reaction. Examples of such catalystsinclude I HgI MgI C HgI, ZnI and the like. Only catalytic amounts ofsuch catalysts need be employed, since it has been found that the amountof catalyst is not an important feature of this invention.

The alkylation process of this invention is generally carried out byreacting an alkyl, aryl or cycloalkyl halide with the finely divided tinor activated tin particles at temperatures of at least about roomtemperature, preferably about 100 to 200 C., and under pressures rangingfrom atmospheric to 150 psi. The alkyl halides are preferably thechlorides, bromides, or iodides having alkyl groups containing from 4 tocarbon atoms, with a preferred carbon atom range being from about 4 to8. Examples of such straight or branched chain alkyl halides include thefollowing:

butyl chloride isobutyl chloride sec-butyl chloride tert-butyl chloridebutyl bromide butyl iodide pentyl chloride isopentyl chloridetert-pentyl chloride pentyl bromide pentyl iodide Z-ethylhexyl chloride2-ethylhexyl iodide n-decyl chloride n-dodecyl chloride from 6 to 12carbon atoms, and illustrative aryl compounds include the following:

chlorobenzene p-dibromobenzene bromobenzene m-diiodobenzene iodobenzenedichlorotoluene chlorotoluene vdibromotoluene bromotoluene diiodotolueneiodotoluene 2-bromonaphthalene o-dichlorobenzene l-chloronaphthalene,etc.

The cycloalkyl halides which may be employed include cyclohexyl bromide,cyclooctyl chloride, and terpene halides.

In general, it is preferred to employ an excess, e.g., at least 50%stoichiometricexcess, of the alkylating agent to produce the desiredalkyl or aryl tin halide compounds. It will be understood, however, thateither lesser or greater amounts of the tin particles may be employeddepending upon the specific reactants, operating conditions, as well asthe elaborateness of the recovery equipment.

In some cases it is desirable, although not essential, to employagitation during the reaction between the alkyl or aryl halides and thefinely divided activated tin particles. Agitation may be accomplished byutilizing conventional equipment and procedures.

As noted above, it is also helpful at times to utiliz a catalyst topromote the reaction. This is particularly so when utilizing the finelydivided tin particles or the tin particles are activated by a priortreatment with mini mal amounts of an alkali metal.

For some purposes it is also helpful to carry out reaction in an inertsolvent. Saturated aliphatic and cyclic hydrocarbon compounds can beemployed, and in general it is preferred to use solvents which can beconveniently separated from the products. It is also important to usesolvents which are stable under the reaction conditions both toreactants and products. Heptane and isooctane are examples of typicalstraight and branched chain aliphatic hydrocarbons which have proven tobe effective. Cyclohexane, toluene, xylenes, benzene, and diphenyl aretypical cycloalkyl compounds, with the former compound being especiallypreferred. Moreover, various inert ether and ester solvents may also beutilized, including ethyl ether, butyl ether, isobutyl ether,tetrahydrofuran, ethylene glycol diethyl ether, tetramethylene glycoldimethyl ether, diphenyl ether, dimethyl phthalate, di-Z-ethylhexylphthalate and the like. Polychloro benzenes and polychloro diphenyls mayalso be used. It is possible, moreover, to operate without the use of anextraneous solvent. Thus, for example, an organotin compound may be usedby itself as the reaction medium.

The reaction product mixture obtained from the foregoing process can besubjected to various procedures to recover the desired alkyl or aryl tinhalide products therefrom. It is possible, for example, to separate theliquid alkyl or aryl tin halides from the solids present in the reactionproduct mixture by filtration or centrifugation and to recover theunreacted tin particles. The alkyl tin halide products can be recoveredfrom the separated liquid phase by distilling off solvents atatmospheric pressure and then recovering the various alkyl tin compoundsby vacuum distillation. It is also possible to precipitate the productsas alkyl or aryl tin oxides, or amine complexes.

More specifically, the recovery procedure can involve the filtration ofthe solids by means of a Buchner-type funnel and washing the solids withcyclohexane with subsequent distillation on a batch basis to remove theexcess alkylating agent and reaction medium followed by cooling to C.,and continuation of the distillation process under a vacuum, forexample, of l-lO mm. This permits removal of traces of solvent below C.and the recovery and, if desired, separation of the various tincompounds obtained at temperatures in the range of 100-160 C. butgenerally l30 0, depending on the length of the carbon chain and thehalides involved as well as on the degree of vacuum achieved. Theproduct mixture obtained can be fractionated to obtain pure products or,alternatively, reheated to temperatures on the order of 210 C., and ifdesired with a calculated amount of stannous halide to convert all ofthe products into a particular alkyl halide.

The solid material can be further treated for recovery of tin values byextraction with water and Washing with dilute acids and alkali torecover any metallic tin by means of subsequent remelting andreatomization operations. From the water soluble portion, halogen valuessuch as bromine or iodine can be recovered by standard methods.

The invention will be more fully understood by reference to thefollowing illustrative embodiments.

EXAMPLE I (A) Finely divided tin free of oxide is prepared by meltingtin of 99.99% purity either continuously or in a batch operation andatomizing it at the rate of 50 lbs./ min. through a sonic atomizingnozzle of the type manufactured by Astrosonics Corp. Helium is used as apropellant and the product is recovered by first separating the coarsematerial by means of a cyclone separator.

The coarse material is then remelted and atomized as described above.The desired material is recovered in suitable filter bags andtransferred to the next operation still under a blanket of helium. Atypical particle size distribution of such a product is 90% belowmicrons, 70% below 5 microns, and a mean particle size of 3.8 microns.

(B) A 500 gm. batch of finely divided tin produced as set forth inExample I(A), is introduced into a stirred 3 neck flash, the stirrer ofwhich closely follows the side. The flask is continuously purged with astream of helium. The flask is then heated by means of an oil bath to atemperature of about 100 C. Granulated sodium is now introduced throughone of the side arms connected to a container, which is also filled withhelium over a period of 10 minutes. The sodium under these conditionsevenly coats the tin and reacts with its surface. The material is nowheated to 150 C. for 2 hours under an atmosphere of helium with stirringand then allowed to cool.

(C) A 500 mm. batch of finely divided tin produced as set forth inExample I(A) is made into a slurry with commercial heptane and isintroduced into a stirred'reactor. To this flask is added a dispersioncontaining 50 gm. of sodium in 200 gm. of heptane, the dispersion havinga grain size finer than 10 microns. The material is stirred for one hourat C. and is then ready for reaction.

EXAMPLE II (A) 300 parts of finely divided tin as produced in accordancewith Example I(A) together with 350 parts of butyl chloride, 150 partsof cyclohexane and 1 part of mercuric iodide are introduced into astainless steel reactor which is then hermetically sealed and heated for4 hours to a temperature of 100 C. The reactor was cooled and uponrecovering the product by filtration and distillation, consisted of 240parts of alkylatin product, containing on the average 38.5% tin andhence, representing a tin utilization of 31%.

(B) The procedure of Example II(A) was repeated except that 500 partsbutyl bromide were substituted for the butyl chloride. The productconsisted of 570 parts of alkyltin product containing 31.8% tin andrepresenting a 60.3% tin utilization.

EXAMPLE III (A) 316 parts of the tin reagent prepared in accordance withthe procedure outlined in Example I(B) but containing 5% sodium wasreacted in a stainless steel reactor with 350 parts of butyl chloride,150 parts of heptane and one part of zinc iodide at 165 C. for 4 hours,at 130 C. for 4 hours, reheating to 165 C. for 2 hours, yielding 6 05parts of product, containing 39.7% tin corresponding to a tinutilization of 80%.

(B) 316 parts of tin reagent prepared in accordance with the procedureoutlined in Example I(B) but containing 5% sodium was reacted in astainless steel reactor with 500'parts of butyl bromide, 150 parts ofheptane and one part of zinc iodide at 110 C. for 8 hours yielding 575parts of product containing 31.5% tin and representing a tin utilizationof 60.5%.

(C) 316 parts of the tin reagent prepared in accordance with theprocedure outlined in Example I(B) but containing 5% sodium was reactedin a stainless steel reactor with 500 parts of chlorobenzene, 150 partsof heptane and one part of zinc iodide at 165 C. for 5 hours yielding472 parts of product averaging 34.0% tin representing a tin utilizationof 53.3%.

(D) 316 parts of the tin reagent prepared in accordance with theprocedure outlined in Example I(B) but containing 5% sodium was reactedin a stainless steel reactor with 500 parts of octyl bromide, 150 partsof heptane and one part of zinc iodide at 165 C. for 5 hours yielding723 parts of product averaging 25.1% tin representing a tin utilizationof 60.5%.

(E) The procedure in Example III(A) was repeated except that 500 partsof butyl bromide were substituted for the butyl chloride. The productconsisted of 775 parts of butyltin bromide containing 32.9% tin andrepresenting of tin utilization.

The above data demonstrate the effectiveness of preparing alkyl tinhalides in accordance with the process of this invention. Thepreparation of butyl tin chloride is shown in Examples II(A) and III(A),whereas the corresponding butyl tin bromide is shown in Examples II(B)and III(B) and (E). Example III further shows the particulareffectiveness of utilizing the sodium activated, finely divided tinparticles in the alkylation reaction. The data further reveal thatimproved tin utilization and product yields can be attained byalternating or cycling the temperatures between 150 to 170 C. and to C.,with the temperature being maintained at each range for at least 2hours.

The alkyl and aryl tin halides which can be prepared in accordance withthe improved process of this invention are known to be useful in thepreparation of stabilizers for plastics such as vinyl chloride,urethanes, and others, as well as being active constituents inantifouling paints, bacteriostatic agents, and the like.

In addition to being used in the alkylation process described andillustrated above, the finely divided tin particles which have beensurface-activated as herein described, are also useful for otherpurposes such as reactions with water and alcohol to produce organic andinorganic tin compounds such as stannous oxide, stannous hydroxide,stannous chloride, stannous alcoholates, stannous stearates, and thelike.

The term alloy as employed throughout this specification and in theappended claims shall mean a mixture or combination of the alkali metaland the tin. As previously set forth, the alkali metal-activated tinparticles of this invention are characterized by the formation of alkalimetal tin alloys on the surface of the tin particles accompanied byalkali metal diffusion into the body of the tin particle to give analkali metal concentration gradient from the center of the particle toits outside surface. It is possible, therefore, to refer to the alkalimetal-activated tin particles as superficial'diifusion alloys.

While particular embodiments of this invention are shown above, it willbe understood that the invention is obviously subject to variations andmodifications without departing from its broader aspects.

What is claimed is:

1. A process for the preparation of organotin halides, which comprisesreacting an organic halide selected from the group consisting of alkyl,aryl, and cycloalkyl halides with finely divided tin the surface ofwhich is activated by treatment with an alkali metal and having aparticle size within the range from about 1 to about 300 microns, in thepresence of an iodine-containing catalyst.

2. The process of claim 1 wherein the catalyst is mercuric iodide.

3. The process of claim 1 wherein the catalyst is zinc iodide.

4. The process of claim 1 wherein the reaction is carried out in thepresence of an inert solvent.

5. The process of claim 1 carried out at a temperature of at least 100C.

6. The process of claim 1 wherein the reaction temperature is alternatedbetween about 150 to about 170 C. and about 125 to about 130 C.

7. The process of claim 1 wherein the finely divided tin has a particlesize within the range from about 5 to 40 microns.

8. The process of claim 1 wherein the alkyl halide contains from 4 to 20carbon atoms.

9. The process of claim 1 wherein the alkyl halide is an alkyl chloride.

10. The process of claim 9 wherein the alkyl chloride is butyl chloride.

8 11. The process of claim 1 wherein the alkyl halide is butyl bromide.

12. The process of claim 1 wherein the alkali metal is sodium.

References Cited UNITED STATES PATENTS 9/1958 Blitzer et a1 260-429.74/1963 Yatagai et al 260-429] OTHER REFERENCES Karantassis et al.:Academie Des Sciences, vol. 205, (1937), pp. 460-461.

HELEN M. McCARTHY, Primary Examiner.

W. F. w. BELLAMY, Assistant Examiner.

